The present invention concerns a method and an apparatus for an anti-spin regulation (ASR) for a vehicle.
Generally, anti-spin regulation (ASR) is based on the detection of wheel speeds while a car is driving or starts driving. When the velocity of one or more driven wheels exceeds the speed of the car, an anti-spin regulation procedure is executed. For this purpose, the slipping wheels are braked by means of a braking system. Additionally or alternatively, the engine speed is reduced. When the slipping of the wheel(s) is reduced, the braking procedure is terminated and/or the engine speed is increased again.
Anti-spin regulation (ASR) principally increases the traction potential of a vehicle. However, in particular in case of anti-spin regulation systems which use brake systems, situations occur, in which during an anti-slip regulation for a slipping driven wheel a further driven wheel tends to slip. This occurs even in case the further driven wheel would principally have a sufficient traction, because an enlarged part of the tractive force is transmitted to this wheel. For example, corresponding situations occur in case of large differences concerning the coefficients of friction for the individual driven wheels.
A way of remedy for the above described situation is disclosed in German Patent Application No. DE 198 37 524.7, filed Sep. 19, 1999. Therein is described a method and apparatus for an anti-slip regulation, or traction control, where one wheel is controlled by building up and reducing braking force in the case of incipient free spinning, braking force being reduced at the controlled wheel when incipient free spinning is to be expected at the uncontrolled wheel.
According hereto, the braking force on the slipping wheel is reduced when a further driven wheel tends to slip.
It is the object of the present invention, to provide an improved method and apparatus for an anti-spin regulation (ASR) for a vehicle.
The object of the present invention is achieved by providing a method for an anti-spin regulation (ASR) for a vehicle, characterized in that a slipping driven wheel is braked by braking means. A further driven wheel is monitored by monitoring means. The further driven wheel is braked by braking means in case a slipping trend is determined by determination means from the monitoring results for said further driven wheel.
The object of the present invention is further achieved by providing an apparatus for an anti-spin regulation (ASR) for a vehicle, in particular eligible for use with the inventive method, characterized in that braking means are implemented for braking a slipping driven wheel. (Monitoring means are implemented for monitoring a further driven wheel.) Braking means are implemented for braking the further driven wheel in case a slipping trend is determined by determination means from the monitoring results for said further driven wheel.
By way of example, here as in the following, any slip xcex is described as:   λ  =                    v        w            -              v        v                    v      v      
wherein vw is the velocity of the slipping wheel and vv is the velocity of the vehicle (or any other suitable reference velocity). Hence, the slip xcex is described as the relative difference of the velocity of the slipping wheel vw and the velocity of the vehicle vv. Moreover, since small slips xcex may be neglected within an anti-spin regulation, only slips xcex of a minimum extent are considered as wheel slips. On the other hand, smaller slips may be considered as slipping trends.
As according to the invention, an anti-spin regulation is provided, according to which slipping occurrences on non-braked, further driven wheels are reduced. Hence, the driving stability is increased. Moreover, the necessity of reduction of the engine speed (which would occur in case two or more driven wheels are slipping) is reduced to a smaller number of cases. In addition hereto, the influence of the anti-spin regulation on the slipping wheel may be increased. On the other hand, in case the further driven wheel cannot be prevented from slipping, a corresponding anti-spin regulation is improved, since a suitable braking force is faster available.
Preferably, the braking force on the slipping driven wheel is reduced when the slipping trend is determined by the determination means for said further driven wheel.
This advantageously combines the invention with a particular suitable method which is known itself as according to the state of the art. Resulting thereof, the advantages of the invention are even intensified.
Within a preferred implementation of the inventive method the slipping trend is determined by the determination means for said further driven wheel by means of comparison of the velocity of the driven wheel to the velocity of the vehicle and comparison of the difference of both velocities (the slipping trend value) to a predefined slipping trend threshold.
This allows an easy implementation of the inventive method. Furthermore, it is possible, to perform the slipping trend detection with ordinary available system components and control means of a anti-slip regulation system.
Advantageously, the anti-spin regulation is executed, when a slipping threshold is exceeded by the difference of the velocity of the slipping wheel and the velocity of the vehicle. The slipping trend threshold is on the same scale below the slipping threshold.
By doing so, it is easy to ensure that by means of consideration of the slipping trend threshold slipping occurrences may be prevented.
The braking force on the further driven wheel may be built up in steps as long as the slipping trend threshold is exceeded, stability thereby being increased.
Preferably, the gradient for building up the braking force on the further driven wheel is modified in accordance with the achieved braking force. Excessive pressure build-up would signify loss of traction, since here split-friction road surface conditions (SH) are assumed.
Within a further preferred implementation of the invention, the braking force on the further driven wheel is reduced in steps when the slipping trend value is below the slipping trend threshold.
By doing so, on the one hand, it is ensured that the braking force is available for a sufficient duration of time. On the other hand, it is ensured, that the braking force is not applied to the further driven wheel for a too long time.